Tirzepatide (Zepbound) currently delivers the most weight loss of any FDA-approved medication, with clinical trial participants losing about 21% of their body weight at the highest dose over 72 weeks. Semaglutide (Wegovy) comes in second at roughly 15% weight loss over a similar period. Both are injectable medications that far outperform older oral options, which typically produce 5–8% weight loss. The “best” drug for you, though, depends on more than raw numbers: cost, insurance coverage, side effects, and whether you can stay on the medication long-term all matter.
How the Top Drugs Compare
The FDA has approved six medications for long-term weight management. They fall into two clear tiers based on effectiveness.
The injectable tier includes Zepbound (tirzepatide) and Wegovy (semaglutide), both given as weekly self-injections. In their landmark clinical trials, people without diabetes taking Zepbound lost between 15% and 21% of their body weight depending on dose, while those on Wegovy lost about 15%. Real-world data from medical records tells a similar story: after one year of continuous use, Zepbound users lost an average of 16.5% of their body weight compared to 14.1% for Wegovy users.
The oral tier includes Qsymia (phentermine-topiramate), Contrave (naltrexone-bupropion), Xenical/Alli (orlistat), and Saxenda (liraglutide, an older daily injection that performs more like the oral drugs). Contrave produces about 5–6% weight loss over a year. Qsymia performs somewhat better, in the range of 7–9%. These are meaningful amounts, but substantially less than the injectables.
Why the Injectables Work So Much Better
The gap between the two tiers comes down to biology. Wegovy activates a single gut hormone pathway called GLP-1, which reduces appetite by signaling fullness to the brain. That alone is powerful, but pushing the dose higher just causes more nausea and vomiting without proportional benefit.
Zepbound activates two pathways: GLP-1 plus a second gut hormone called GIP. The combination does more than just double down on appetite suppression. The GIP component appears to improve how the body handles insulin and may reduce the nausea that limits GLP-1 drugs, which means patients can tolerate doses that drive deeper weight loss. It also seems to trigger weight loss through mechanisms beyond simply eating less, though researchers are still sorting out exactly how.
A next-generation drug called retatrutide adds a third target: the glucagon receptor. Glucagon tells the body to burn stored energy, essentially raising the calorie-burning side of the equation rather than just lowering the appetite side. In a phase 2 trial published in the New England Journal of Medicine, participants on the highest dose of retatrutide lost 24.2% of their body weight in just 48 weeks, with 83% losing at least 15%. That drug is still in clinical trials and not yet available, but it illustrates where the field is heading.
Side Effects Across the Options
Gut-related side effects are the main drawback of injectable weight loss drugs. Nausea, vomiting, diarrhea, and constipation are common, especially during the first few months as the dose gradually increases. Most people find these symptoms ease over time. In rare cases, more serious digestive slowdowns occur.
The oral medications have their own profiles. About one-third of people taking Contrave experience nausea, and roughly one in five deals with constipation. Headache, dizziness, and insomnia also show up frequently. Qsymia can cause tingling in the hands and feet, concentration difficulties, and taste changes, and it carries a risk of birth defects, so it requires pregnancy prevention measures. Orlistat works differently from all of these, blocking fat absorption in the gut, which means its main side effects are oily stools and urgency after eating fatty foods.
Phentermine, an older stimulant approved only for short-term use (typically 12 weeks), is still widely prescribed. A large study of nearly 14,000 adults found that people using it for more than 12 months lost 7.4% more weight than short-term users, with no increased risk of cardiovascular events or death. It remains limited by its stimulant properties: elevated heart rate, insomnia, and the potential for dependence.
What Happens When You Stop
This is the most important consideration many people overlook. Weight loss medications treat obesity as a chronic condition, similar to how blood pressure drugs treat hypertension. When you stop taking them, the weight tends to come back.
The data is sobering. In clinical trials, people who stopped semaglutide regained over 40% of their lost weight within just 28 weeks. Those who discontinued tirzepatide regained more than 50% of their weight loss over a year. A meta-analysis found that the longer someone goes without the drug, the more weight returns: studies tracking people for more than six months after stopping showed an average regain of about 7.3 kilograms, compared to 2.5 kilograms in shorter follow-up periods.
This means the “best” weight loss drug is one you can realistically stay on. A medication producing 21% weight loss means little if you can only afford it for six months.
Cost and Insurance Coverage
Cost is the biggest barrier to the injectable medications. Wegovy was originally priced above $1,300 per month, though Novo Nordisk now offers it directly to consumers for about $499 per month. Zepbound sits in a similar range. Without insurance, you’re looking at $500 or more each month, indefinitely.
Insurance coverage varies widely and is getting more complicated, not less. GLP-1 drugs have become the single largest pharmacy expense for many employers, with spending increasing 50% year over year in some cases. In response, companies are tightening access. About one in three employers that cover these drugs now require enrollees to meet with a dietitian, therapist, or participate in a lifestyle program before coverage kicks in. Some have set BMI cutoffs at 35 or higher, well above the FDA’s threshold of 30. Others have stopped covering them for weight loss entirely.
If your insurance denies coverage, the older oral medications become more relevant. Contrave and generic phentermine-topiramate cost a fraction of the injectables. They produce less weight loss, but 5–8% of body weight is still clinically meaningful and enough to improve blood pressure, blood sugar, and joint pain.
Who Qualifies
FDA guidelines set the eligibility threshold at a BMI of 30 or above, or a BMI of 27 or above with at least one weight-related health condition such as high blood pressure, type 2 diabetes, or high cholesterol. Four of the approved medications (Wegovy, Qsymia, Saxenda, and Xenical) are also approved for adolescents ages 12 and older. Zepbound and Contrave are currently approved for adults only.
Choosing the Right Medication
If maximum weight loss is the priority and cost isn’t a barrier, Zepbound has the strongest evidence. It outperforms Wegovy both in clinical trials and real-world use, and the dual-hormone mechanism appears to offer a better balance of effectiveness and tolerability. Wegovy is a close second and has a longer track record, plus approval for adolescents.
If you prefer pills over injections, or if injectables aren’t covered by your insurance, Qsymia generally produces more weight loss than Contrave. Contrave is a reasonable option for people who also struggle with cravings or have a history of mood-related eating, since its components affect reward pathways in the brain.
If you’ve been prescribed a GLP-1 drug and the nausea is difficult to manage, know that slow dose escalation makes a real difference. Most treatment plans start at a low dose and increase every four weeks, giving your body time to adjust. The side effects are typically worst in the first two to three months and improve significantly after that.